1. Field of the Invention
The present invention is an improvement of the applicant's previously patented inventions, U.S. Pat. No. 4,132,253 and U.S. Pat. No. 4,319,931. All are in the field of woodworking machines and methods, particularly in the field of gaining pallet stringers. The gaining operation, herein called notching, is done to permit the fork of a lift truck to pick up a pallet when the fork is normal to the stringers as well as when it is parallel. The present invention's improvement makes it possible to produce rounded corner notches in the same time now required for sharp-cornered notches and at a savings in energy requirements compared with present machines. The rounded corner notch is one with fillets on interior corners. A fillet is defined as a concave junction formed where two surfaces meet and is called a rounded corner herein.
2. Description of the Prior Art
The closest prior art known to the applicant are his U.S. Pat. No. 4,132,253 and U.S. Pat. No. 4,319,931. The patent is for a machine to cut notches in pallet stringers comprising, like the present invention, a base frame, a conveyor means for supporting and driving the stringers through the machine, a first cutting means for making at least four vertical cuts in each stringer, a second cutting means for for making a horizontal cut at top ends of the vertical cuts so positioned that a portion of the stringer between innermost vertical cuts is first cut away allowing arbor of the second cutting means to pass through the stringer while cutting away remaining portions between outermost vertical cuts. This machine makes no provision for producing a rounded corner.
The applicant's U.S. Pat. No. 4,319,931 is for a method for notching the stringers of an assembled pallet. Likewise it makes no provision for producing a rounded corner.
Earlier art includes U.S. Pat. No. 134,588, Brunjes and Benneckendorf, showing a machine for cutting a large piece of sugar into small blocks by using a gang of circular saws to cut a grid of grooves in the block and a cutoff saw at right angles to previous cuts to produce the small blocks. This machine is not capable of removing a block from an object while leaving the remainder of the object.
Goethe's U.S. Pat. No. 726,673 has gangs of vertical saw blades that cut notches not any wider than the saw blade thickness and reduce all removed material to sawdust.
Litz's U.S. Pat. No. 784,409 has gangs of vertical saw blades and a horizontal cutoff blade but is limited to producing blocks and cannot produce notches.
Weigand's U.S. Pat. No. 1,098,465 shows a mitering machine that cuts a mitered notch in a workpiece 24 after a mortise has been cut. The mortise 40 makes possible the passage, in steps, of an arbor 9 of a horizontal saw 10 through the workpiece 24. This machine will not make the notches required on pallet stringers because the mortise would weaken the stringer and the miter cuts would take up too much room on the underside of the pallet. This patent makes no provision for a rounded corner notch.
A machine now used for cutting notches with rounded corners in pallet stringers is shown in Short's U.S. Pat. No. 3,470,924. The circular cutting head 65 cuts out the entire notch by reducing it to sawdust. This takes more energy and time than the applicant's invention.
Well's U.S. Pat. No. 3,664,394 and Siel's U.S. Pat. No. 3,735,787 both have a group of adjoining cutters capable of cutting a rounded notch in pallet stringers by cutting all removed wood into sawdust and chips. These two machines do not have the energy-saving and time-saving capabilities of the applicant's invention, nor its useful waste product. Short, Wells, and Seil illustrate various ways of making a rounded corner notch.
The present state of the art does not include machines, other than experimental ones based on the applicant's invention, that will cut a rounded corner notch in pallet stringers using considerably less energy and time than the described prior art of Short, Wells, and Seil and produce a waste product remainder that is about eighty percent wood blocks. The wood blocks are more valuable than sawdust which comprises one hundred percent of the waste product remainder of prior art machines and methods. The term sawdust in this specification includes wood chips.